We require that an input directed graph is condensed into a DAG, where each vertex is associated with its pre-order and post-order numbers. One may run this C++ program to transform a directed graph (e.g., the Web-Stanford dataset on the download page), where one needs to provide the number of vertices and edges (see here for the numbers of Web-Stanford), and the smallest vertex ID (e.g., 0 for Web-Stanford). The processed data can then be put to HDFS (we assume path "/reach") for later processing by Quegel.